It is known to sterilize articles with a vaporized chemical sterilant, such as hydrogen peroxide, peracetic acid and glutaraldehyde. Wu et al. U.S. Pat. No. 6,365,102, incorporated herein by reference, describes a hydrogen peroxide/gas plasma sterilization system comprising a vacuum chamber, source of hydrogen peroxide vapor and a source of RF energy to create a plasma. Such systems marketed under the name STERRAD® are available from Advanced Sterilization Products division of Ethicon, Inc. in Irvine, Calif.
Jacobs et al., U.S. Pat. No. 6,325,972 found that when the water has a higher vapor pressure then the sterilant component of the solution, such a solution of hydrogen peroxide, that by controlling the temperature and pressure at which the solution is vaporized the water can be preferentially drawn off from the solution to increase the concentration of the sterilant in the solution. If the water is exhausted from the system during this process it leaves a higher concentration of the sterilant in the system. The higher concentration of sterilant during the phase in which the vapor phase sterilant contacts articles to be sterilized leads to increased efficiency in the sterilization process.